Break It Down: Decomposition
Split compounds using heat, light, or electricity.
What this lesson covers
Why it matters
A single compound splits into two or more simpler substances under heat, light, or electricity. Watch one molecule unravel into distinct products.
The idea in plain words
Balance check: Confirm the atoms on both sides of CaCO₃ → CaO + CO₂.
Predict first
When calcium carbonate is heated strongly, what happens to the solid?
Thermal decomposition breaks CaCO₃ into CaO and CO₂.
- It melts into a liquid
- It breaks down into calcium oxide and carbon dioxide — correct
- It turns into calcium metal and oxygen gas
- Nothing happens; it is stable
What you do
Run all three. Notice what drives each apart — strong heat, electricity, or a catalyst that changes the rate (a catalyst is a helper, not an energy source).
Check yourself
How do you confirm the gas produced in the thermal decomposition of CaCO₃?
CO₂ turns limewater milky due to the formation of insoluble calcium carbonate.
What is the role of phosphoric acid in the decomposition of hydrogen peroxide?
Phosphoric acid is a negative catalyst (inhibitor) that slows the decomposition of H₂O₂.
Why is electrolysis used for the decomposition of NaCl?
Molten NaCl is an ionic compound that requires electrolysis to decompose into Na and Cl₂.
- It relights a glowing splint
- It turns limewater milky — correct
- It burns with a pop
- It acts as a positive catalyst to speed it up
- It acts as a negative catalyst to slow it down — correct
- It reacts to form water and oxygen directly
- Because NaCl is a covalent compound
- Because it requires electrical energy to break the ionic bonds in molten state — correct
- Because heat alone is sufficient